要使用C# Netty實現數據壓縮，你需要遵循以下步驟：

1. 添加依賴項

首先，你需要在項目中添加Netty和壓縮庫的依賴項。對于.NET Core或.NET 5/6，你可以使用以下依賴項：

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.72.Final</version>
</dependency>
<dependency>
    <groupId>org.lz4</groupId>
    <artifactId>lz4-java</artifactId>
    <version>1.8.0</version>
</dependency>

2. 創建壓縮和解壓縮的處理器

接下來，你需要創建兩個處理器，一個用于壓縮數據，另一個用于解壓縮數據。

using System;
using System.IO;
using System.Threading.Tasks;
using io.netty.buffer.ByteBuf;
using io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.compression.ZlibDecoder;
import io.netty.handler.codec.compression.ZlibEncoder;

public class CompressionHandler : ChannelInboundHandlerAdapter
{
    private readonly bool _compress;

    public CompressionHandler(bool compress)
    {
        _compress = compress;
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, object msg)
    {
        ByteBuf input = (ByteBuf) msg;

        if (_compress)
        {
            ByteBuf compressed = compress(input);
            ctx.writeAndFlush(compressed);
        }
        else
        {
            ByteBuf decompressed = decompress(input);
            ctx.writeAndFlush(decompressed);
        }

        input.release();
    }

    private ByteBuf compress(ByteBuf input)
    {
        using (ZlibEncoder encoder = new ZlibEncoder(1024, 8, 1))
        {
            return encoder.encode(input);
        }
    }

    private ByteBuf decompress(ByteBuf input)
    {
        using (ZlibDecoder decoder = new ZlibDecoder(1024, 8, 1))
        {
            return decoder.decode(input);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
    {
        ctx.close();
        cause.printStackTrace();
    }
}

3. 創建Netty服務器和客戶端

現在你可以創建一個使用上述壓縮處理器的Netty服務器和客戶端。

using io.netty.bootstrap.Bootstrap;
using io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class NettyServer
{
    public static async Task StartAsync(int port)
    {
        EventLoopGroup serverGroup = new NioEventLoopGroup();
        EventLoopGroup clientGroup = new NioEventLoopGroup();

        try
        {
            Bootstrap serverBootstrap = new Bootstrap
            {
                Group = serverGroup,
                Channel = NioServerSocketChannel.class,
                ChildInitializer = (channel, context) =>
                {
                    channel.pipeline().AddLast(new StringDecoder());
                    channel.pipeline().AddLast(new StringEncoder());
                    channel.pipeline().AddLast(new CompressionHandler(true));
                    channel.pipeline().AddLast(new MyServerHandler());
                }
            };

            ChannelFuture serverFuture = await serverBootstrap.BindAsync(port);
            serverFuture.Sync();

            Console.WriteLine($"Server started on port {port}");

            while (true)
            {
                // Wait for client connection
            }
        }
        finally
        {
            serverGroup.ShutdownGracefully();
            clientGroup.ShutdownGracefully();
        }
    }
}

public class NettyClient
{
    public static async Task StartAsync(string serverAddress, int port)
    {
        EventLoopGroup group = new NioEventLoopGroup();

        try
        {
            Bootstrap clientBootstrap = new Bootstrap
            {
                Group = group,
                Channel = NioSocketChannel.class,
                ChildInitializer = (channel, context) =>
                {
                    channel.pipeline().AddLast(new StringDecoder());
                    channel.pipeline().AddLast(new StringEncoder());
                    channel.pipeline().AddLast(new CompressionHandler(false));
                    channel.pipeline().AddLast(new MyClientHandler());
                }
            };

            ChannelFuture clientFuture = await clientBootstrap.ConnectAsync(serverAddress, port);
            clientFuture.Sync();

            Console.WriteLine($"Connected to server {serverAddress}:{port}");

            while (true)
            {
                // Send and receive messages
            }
        }
        finally
        {
            group.ShutdownGracefully();
        }
    }
}

現在你可以使用NettyServer.StartAsync和NettyClient.StartAsync方法啟動服務器和客戶端。注意，你需要實現MyServerHandler和MyClientHandler類來處理接收到的消息。